1. Field of the Invention
This invention relates to a method for treating a subterranean, fines-containing formation penetrated by a well to improve, maintain and preserve the permeability of the formation. More particularly, the invention relates to such a method wherein movement of the fines and swelling of water-sensitive fines is minimized.
2. Description of the Prior Art
In producing or recovering fluids from subterranean formations containing fines, such as silt-sized or smaller particles, it is often the experience that these very fine particles are subject to movement by the fluid even when the fluid is flowing at a relatively low rate. Where a large volume of fluid is forced to flow through such a silty or dirty formation, the very fine particles tend to be carried along until they become lodged in a pore throat, e.g., the smaller interstices between the grains of the formation. This at least partially plugs the openings and reduces the permeability of the formation. A permeability impairment due to the movement of such particles is often a major problem in the operation of fluid injection wells and fluid production wells. Also, certain types of water-sensitive clay fines which can be present in the formation, for example montmorillonite, can swell and decrease the permeability of the formation if the fluid passing therethrough is or contains water.
Various treatments have been proposed to minimize damage to formation permeability by fine particles. Such treatments have included the injection of zirconium oxychloride to stablize clays, converting clays from the swelling sodium or lithium form to another cation form which does not swell as much, and injection of various amines or hydroxyaluminum solutions.
Further, it is known to inject particular organosilanes into subterranean formations as a component of various treating agents for various purposes. Thus, U.S. Pat. No. 3,286,770 to Knox et al. teaches a method for rendering formations preferentially oil-wettable so as to increase the flow rate of water therethrough. The method involves injecting into the formation a treating agent comprising certain organohalogensilanes in a water-soluble solvent. The organohalogensilane reacts with silica surfaces or sand in the formation to form a polymer and render the formation oil-wettable.
U.S. Pat. No. 2,633,919 to Bauer et al. describes a method for increasing oil production from a well wherein the formation is first dried as by heating or injection of a solvent wash such as alcohol. Next there is injected into the formation a silicone-forming agent, for example, a mono-, di-, or trialkyl, or -aryl silicon halide, or corresponding ester thereof, to form a solid silicone polymer which is bonded to the surface of the formation.
While these and other treatments have met with some success in particular applications, the need exists for a further improved well treating process to minimize the reduction in permeability that can occur when a fluid passes through a formation which contains moveable and/or swellable finely divided particles.
Accordingly, a principal object of this invention is to provide a method for reducing the permeability damage to fines-containing subterranean formations due to passage of a fluid therethrough.
It is another object to provide a method of inhibiting permeability impairment due to the movement or swelling of very fine particles within a porous formation.
It is still another object to provide a method for stabilizing fines-containing formations.
It is a further object to coat the fines of a fines-containing formation to bind them in position and minimize contact between the fines and fluids subsequently passed through the formation.
It is a still further object to provide such a method without first drying the formation to remove water from the area to be treated.
It is a still further object to provide such a method without injecting water into the formation at the conclusion of the treatment.
Other objects, advantages and features of this invention will become apparent to those skilled in the art from the following description and appended claims.